Nelson Racing Engines Small Block Chevy - Project F-Bomb!

Written
by
David Freiburger
on February 14, 2007 Contributors: Wes Allison1,000 hp You Can Drive Every Day and 1,500 hp on Weekends! Here's How Nelson Racing Engines Did It With HOT ROD's 406ci Small-Block.

There's a special moment on the dyno when you know that junk is makin' power. It's a certain shriek, a different rattle of the windows, and -cliched but true-a palpable movement of the earth. It all happened for us with this small-block at Nelson Racing Engines: 1,000 hp on 91-octane, 1,500 hp on race gas, 900-plus lb-ft everywhere we looked. That's all under 6,000 rpm, and it idles at just 700 rpm under load with 12-15 inches of vacuum.

This is one of the most powerful engines HOT ROD has ever been a part of. It's also the tamest in recent memory, which is entirely the point. Both Tom Nelson (Nelson Racing Engines) and Rick Head (Innovative Turbo Systems) have been trying to open our eyes to this kind of satisfaction for years, and while we've previously been disparaging of the complexity and expense of turbo power, there's no question it offers the best of both worlds: total driveability matched with ungodly power. It's the ultimate dream for all the readers who have demanded to see more streetable engines in our pages, yet it satisfies the power lust of every Drag Week(tm) racer who needs 8-second power that can go the distance.

Nelson has anchored his reputation on fulfilling this paradoxical craving. He spent a year of midnights on his DTS dyno hashing out his perfect setup with a personal goal of becoming the go-to guy for anyone demanding zero-hassle twin-turbo power. He's delivered engines for Boyd Coddington, Steve Strope, Mark Stielow, and many others. His customers are mostly guys who need to pull the engine out of the box, stab it in the car, throttle it blindly, and never have anything go wrong. As such, he's learned a bunch about seamless power and turnkey reliability, and he'll share it here along with most of his evolution of speed secrets. While this engine is a small Chevy, turbo packages are also available for big and small Chevy, Ford, and Mopar engines. But don't think it's even close to cheap. Our small-block would be $35,000 complete with all the custom stainless tube bending, the complete Electromotive engine management system, and the Aeromotive fuel system.

This particular engine will be Nelson's opportunity to test his own product with abandon. This 406 is destined for HOT ROD's Project F-Bomb, a '73 Camaro being built at Nelson as both a daily driver and as a serious threat for street-car racing events, and if everything comes together perfectly on a very short schedule, Tom will drive it and race it on Drag Week(tm). This should be fun.

Short-Block

Remember a few years ago when HOT ROD had a test-mule engine called the Anvil? That short-block was where this turbo engine started, though by the time Nelson was finished, there was nothing left of it but the beefy Motown block from World Products (we would never attempt these power levels with a stock Chevy block) and the Lunati Pro Mod Super Duty 6.00-inch rods. The Anvil had a 3.50-inch-stroke Lunati crank to begin with, but Nelson wanted more inches for low-end driveability in no-boost situations, so he got 406 ci by swapping to a 3.750-inch Lunati Pro Series 4340 forged-steel crank. These days, Nelson actually builds more 427-inch combos (4.125x4.00-inch), and he uses billet rods rather than top-quality forgings, just to be safe.

For oiling, Nelson relies on the improved priority-main system in the Motown block and uses a stock-type Speed-Pro oil pump, feeling that an engine under 6,000 rpm does not need greater output. Nelson uses Kendall nonsynthetic 40W racing oil and prefers Billet Fabrication custom oil pans to prevent windage and aeration for both power and turbo longevity.

6/25For bearing durability, Nelson's favorites are Clevite H-series in a half-groove design on the mains. The H-series has a thinner, harder surface coating that seems to better withstand extreme boost pressures, and he's seen them look like new with 30-plus dyno pulls at 1,200 hp. Nelson uses the softer P-series bearings in lower-power applications, but the surface tends to flake at 1,000-plus horsepower.

Heads And Gaskets

For simplicity, the engine uses regular, bolt-on-style, 23-degree heads, but they're serious ones: Brodix 11X models with 227cc CNC-ported intake runners (PN 1110005, bare). Nelson feels they have the best balance of flow and durability (valve job, deck thickness, valveguide material) for the application, and while there are 23-degree heads with better peak flow numbers, these have the area under 0.600 inch lift he's looking for. The only thing he has to do is chase all the spark-plug threads before installation. While our heads use the regular exhaust-flange pattern, Nelson has subsequently started using the spread-port pattern offered by Brodix on the same 11X heads. The valves are stainless on the intake but require Inconel on the exhaust for long life with the turbos.

Perhaps the most common turbo-engine failure is a blown head gasket. While many racers have gone to new multilayer steel head gaskets, Nelson sticks with a custom process using wire rings and SCE Pro Copper head gaskets that has rarely seen a failure. Here's how it works. He learned this from Larry at HP Works and swears it solves every head-sealing problem up to 35 psi boost.

Cylinder-Head Specs

7/25Here's the key to this engine being as tame as it is: a dinky camshaft with a wide lobe sep. All the info for this single-pattern Comp Cams custom roller is in the specs box above. It's used with Comp's regular heavy-duty solid roller lifters, Pro Magnum pushrods, and 1.65:1 Pro Magnum roller rockers. Nelson prefers not to use titanium retainers since he's seen them gall after many miles, so he uses Comp PN 741-16 steel retainers with the Comp PN 939 springs and PN 4770-16 locator cups in the Brodix heads.

These numbers are flowed at 28 inches of water, and while these are advertised numbers provided by Brodix, Nelson says he has sometimes seen them flow as high as 300 cfm on the intake on his own bench. The exact heads used on our engine were not tested.

Induction

11/25Finally, Nelson torques the heads into place, then chills with a Diet Coke while heat guns are set on full blast, blowing into the water passages for half an hour to fully heat the heads. The gasket goop softens up at which point the heads are loosened (it now takes just 45 ft-lb to break the bolts loose) and retorqued for the final time while still hot. It's usually the last time the bolts will need to be checked.<BR><BR>

The intake manifold of choice varies depending on customer request. The turbo engine can be built with an as-cast four-barrel intake converted to EFI, though Nelson prefers to use Holley Stealth Ram box/runner intakes for smaller engines or lower budgets and custom sheetmetal intakes for the more serious engines. Our 406 used a custom-fabricated aluminum setup from Hogan's Racing Manifolds, about $3,200 on its own. At press time, Nelson was close to releasing his own all-billet intake with longer, more aggressively tapered runners that he has found to work on his bigger 427ci small-block crate engines.

Fuel & Spark

For fuel and spark control, Nelson prefers Electromotive's Total Engine Control management system, the TEC3r. He's found it gives him improved bearing life, probably due to the precision of the system's ignition control that's said to prevent crank bending and vibration with its computerized, distributorless spark that's triggered via crank angle rather than being time-based. Regardless of the engine's rate of acceleration, the spark occurs exactly at the programmed point. The Electromotive XDi ignition is available separately, but the TEC3r also includes fuel control that Nelson uses in sequential mode. Other features include rev limiting (with timing and current reduction, not cylinder dropping), data-logging, and multiple accessory triggers. Nelson tunes the TEC3r on the dyno and can further tune customers' cars remotely via the Internet once the engines are installed.

12/25Here's the Hogan's box-ram intake, totally scienced out with all the brackets and bungs for a clean EFI installation. It features an entirely open plenum area; the runners do not extend into the box. We chose a purposeful satin finish for the engine, though Nelson can deliver them polished as well. The fabricated valve covers are from Jeff Johnston's Billet Fabrication.

Fuel delivery is handled by 83 lb/hr Deeds injectors fed by fuel-system components from Aeromotive (no relation to Electromotive). On the dyno, the Eliminator pump was used (PN 11104) along with the boost-referenced "R2D2" Pro-Series EFI regulator. With base fuel pressure set to 52 psi, the boost-referenced regulator increases fuel pressure in a 1:1 ratio with manifold pressure so that at 10 psi turbo boost, the total fuel pressure climbs to 62 psi. Without increasing fuel pressure to compensate for boost, the net fuel pressure would be reduced by the amount of the manifold pressure; for example, 52 psi fuel pressure and 10 psi boost pressure would net 42 psi of fuel at the injectors.

Turbo & Plumbing

Most engine builders get secretive about cam specs and such, but we've spilled all those guts in this story. The annoying thing about Tom Nelson is that he won't share his turbo specs beyond telling us they're 72mm, they are not ball-bearing style, and they're from Innovative Turbo Systems. We'll add that the exhaust trim and housing configuration are what most people-including Rick Head of Innovative-consider pure race stuff, too serious for street or strip use under 1,000 hp. But Nelson swears that his happy customers can't be wrong.

As for the plumbing, Nelson has also made jigs to create turbo headers for many popular applications and uses SPD components; the company has every tubing and plumbing widget you can dream of. The headers for this engine use 314 stainless flanges with 321 stainless for the balance of the exhaust. The 321 is the topline stainless steel for maximum cracking resistance and was the only choice for longevity with this street engine, though it's very expensive. Inconel is an even stronger and pricier option, though not deemed necessary for this application.

16/25The Electromotive TEC3r box measures 6.400x5.500x1.670 for easy mounting. The ignition control uses a distributorless setup that normally uses paired coils (one coil per two cylinders, waste-spark style), though Nelson programs for coil-on-plug (one coil per cylinder) for neater spark-plug wiring and coil mounting. A three-bar MAP sensor proved suitable for all the tuning levels with the 83 lb/hr injectors.

Dyno Test

Thing is, this isn't a race engine. So how come it can make 1,500 hp? Big-time turbo boost. There are certainly cheaper ways to make that kind of power, but the hook is the driveability. Whether it's in 760hp or 1,500hp trim, the idle quality is the same: 700 rpm with typical torque-converter load and 12-15 inches of vacuum thanks to the small camshaft and 115-degree lobe separation angle. Nelson says the 427s with the same cam and 116-degree LDA are even tamer. It's got true drive-anywhere idle and cruising quality backed with components intended to keep it alive when you step up the violence.

Speaking of which, check the hideous power this thing makes on the DTS dyno at Nelson Racing Engines, all corrected for standard temperature and pressure and tested at 145 degrees of water temp. The "Wow" tune-up with a 91-octane-friendly 7 psi boost delivers 724 lb-ft at a low 4,800 rpm and 769 hp at an also-low 6,000 rpm. That would be enough to shout about from any 406ci, pump-gas small-block ... except you can turn it up. The "Brutal" curve is at about the limit of safe 91-octane territory at 14.5 psi of intercooled boost, but when you want it, you can have an absolutely punishing torque curve that rarely dips below 900 lb-ft, and you can brag of 1,000-plus horsepower every day.

17/25The Electromotive trigger wheel uses a 60-minus-2 configuration; TDC is set by aligning the pickup with the trailing edge of the 11th tooth after the gap in the wheel (arrow). This triggers the computer's spark-timing control based on crank angle, effective regardless of rpm. Nelson now has his own ATI dampers with integral trigger wheels for even cleaner, more reliable installations.<BR><BR><BR><BR>

The "Unreal" power curve is on 110-octane race fuel, and it began to push the limits of the 83 lb/hr injectors as the engine delivered the nastiest, table-flat, 1,000 lb-ft torque curve you can imagine, plus 1,165 hp at the top end. Finally, cuz Nelson can't leave well enough alone, he swapped to 160 lb/hr injectors from Deeds, retuned the TEC3r, cranked up two Aeromotive pumps, and made "F-Bomb" power: 1,502 hp at peak and never a drop less than 1,000 lb-ft. That's cramming air past the limit of what this engine is really designed to do, but the daily driveability combined with the ability to step it up for some crazy weekends is just pure insanity.

The Full Nelson

Tom Nelson grew up around road racing and got his start in karts. His first car was an IROC Camaro, and it didn't take long for him to scatter it on nitrous since nothing else seemed to make it go any quicker. His dad forced him to rebuild it on his own, which became his introduction to the guts of an engine. The interest led him to eventually buy his own machine shop, but, as he said, "I got sick of decking grandma engines 15 hours a day just to pay the rent," and he decided to go performance only. Nelson Racing Engines was born.

His next venture is to take his turbo crate engines and, with the help of Scott's Customs and other local gearhead shops, build entire cars around them. HOT ROD's F-Bomb Camaro will be the first of those efforts. It will be several issues down the road before we get it rolling, but watch for it.

21/25For awesome video of the engine running on the dyno, go to www.nelsonracingengines.com. Note that the electric water pump seen on the engine in other photos was not actually used in dyno testing, as the electric noise it produces does not work with the TEC3r engine management.

22/25

Turbo Basics1. This is what the 321 stainless header looks like after glowing red a few times and before the ceramic coating by Extreme Heat Coating.2. The header uses a special SPD collector for turbo applications.3. A V-band clamp connects the header to the intermediate pipe and allows the user to rotate the turbo assembly into position and lock it down.4. This is the Innovative Turbo Systems ProGate 42mm wastegate. It has a diaphragm that is spring-loaded on one side and referenced to manifold pressure on the other. Changing the spring pressure allows the gate to open at the desired point, bleeding off exhaust pressure to slow the turbo and control peak boost.5. Oil feed from engine to turbo.6. This is the air inlet, leading to the compressor side of the turbo.7. This is the air outlet, feeding air through the intercooler then to the engine.8. Oil drain back to the pan.9. The cast-iron turbine section is where the exhaust pressure spins the wheel inside the turbocharger.10. Another V-band clamp secures the downpipe to the turbo; the downpipe connects to the rest of the exhaust system.11. The oxygen sensor is located in the downpipe.